As is well known to those skilled in the art, hydrocarbon lubricating oils must be formulated, as by addition of various additives, to improve their properties.
In the case of lubricating oils, typified by those employed in railway, automotive, aircraft, marine etc. service, it is found that they become degraded during use due inter alia to formation of sludge which may be generated by deterioration of the oil or by introduction of undesirable components from other sources including the fuel or the combustion air. In order to maintain and improve the properties of the lubricating oil, various additives have heretofore been provided; and these have been intended to improve the viscosity index, dispersancy, oxidative stability, etc.
It is an object of this invention to provide an additive system which imparts to lubricating oils these improved properties of viscosity index, dispersancy, oxidative stability, etc. Other objects will be apparent to those skilled in the art.
Also, it is noted a reduction in cost of lubricating oils can be made by using an additive which improves not only the viscosity index, but is also effective as dispersant and antioxidant. Such an additive can be prepared by incorporating dispersant and antioxidant units onto ethylene-propylene copolymer (EPM) or ethylene-propylene-diene terpolymers (EPDM). In particular, one or two monomers, with dispersant and antioxidant functionality, may be grafted onto the polymer to produce such multifunctional VI improver. In our invention, new dispersant and antioxidant VI improver is prepared by grafting only one monomer.